* them first, so we also have a way of "reflecting" them into the Guest as if
* they had been delivered to it directly. :*/
#include <linux/uaccess.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
#include "lg.h"
+/* Allow Guests to use a non-128 (ie. non-Linux) syscall trap. */
+static unsigned int syscall_vector = SYSCALL_VECTOR;
+module_param(syscall_vector, uint, 0444);
+
/* The address of the interrupt handler is split into two bits: */
static unsigned long idt_address(u32 lo, u32 hi)
{
{
/* Stack grows upwards: move stack then write value. */
*gstack -= 4;
- lgwrite_u32(lg, *gstack, val);
+ lgwrite(lg, *gstack, u32, val);
}
/*H:210 The set_guest_interrupt() routine actually delivers the interrupt or
* it). */
static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err)
{
- unsigned long gstack;
+ unsigned long gstack, origstack;
u32 eflags, ss, irq_enable;
+ unsigned long virtstack;
/* There are two cases for interrupts: one where the Guest is already
* in the kernel, and a more complex one where the Guest is in
if ((lg->regs->ss&0x3) != GUEST_PL) {
/* The Guest told us their kernel stack with the SET_STACK
* hypercall: both the virtual address and the segment */
- gstack = guest_pa(lg, lg->esp1);
+ virtstack = lg->esp1;
ss = lg->ss1;
+
+ origstack = gstack = guest_pa(lg, virtstack);
/* We push the old stack segment and pointer onto the new
* stack: when the Guest does an "iret" back from the interrupt
* handler the CPU will notice they're dropping privilege
push_guest_stack(lg, &gstack, lg->regs->esp);
} else {
/* We're staying on the same Guest (kernel) stack. */
- gstack = guest_pa(lg, lg->regs->esp);
+ virtstack = lg->regs->esp;
ss = lg->regs->ss;
+
+ origstack = gstack = guest_pa(lg, virtstack);
}
/* Remember that we never let the Guest actually disable interrupts, so
* the "Interrupt Flag" bit is always set. We copy that bit from the
- * Guest's "irq_enabled" field into the eflags word: the Guest copies
- * it back in "lguest_iret". */
+ * Guest's "irq_enabled" field into the eflags word: we saw the Guest
+ * copy it back in "lguest_iret". */
eflags = lg->regs->eflags;
if (get_user(irq_enable, &lg->lguest_data->irq_enabled) == 0
&& !(irq_enable & X86_EFLAGS_IF))
/* Now we've pushed all the old state, we change the stack, the code
* segment and the address to execute. */
lg->regs->ss = ss;
- lg->regs->esp = gstack + lg->page_offset;
+ lg->regs->esp = virtstack + (gstack - origstack);
lg->regs->cs = (__KERNEL_CS|GUEST_PL);
lg->regs->eip = idt_address(lo, hi);
kill_guest(lg, "Disabling interrupts");
}
-/*H:200
+/*H:205
* Virtual Interrupts.
*
* maybe_do_interrupt() gets called before every entry to the Guest, to see if
/* Look at the IDT entry the Guest gave us for this interrupt. The
* first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip
* over them. */
- idt = &lg->idt[FIRST_EXTERNAL_VECTOR+irq];
+ idt = &lg->arch.idt[FIRST_EXTERNAL_VECTOR+irq];
/* If they don't have a handler (yet?), we just ignore it */
if (idt_present(idt->a, idt->b)) {
/* OK, mark it no longer pending and deliver it. */
* the stack as well: virtual interrupts never do. */
set_guest_interrupt(lg, idt->a, idt->b, 0);
}
+
+ /* Every time we deliver an interrupt, we update the timestamp in the
+ * Guest's lguest_data struct. It would be better for the Guest if we
+ * did this more often, but it can actually be quite slow: doing it
+ * here is a compromise which means at least it gets updated every
+ * timer interrupt. */
+ write_timestamp(lg);
+}
+/*:*/
+
+/* Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent
+ * me a patch, so we support that too. It'd be a big step for lguest if half
+ * the Plan 9 user base were to start using it.
+ *
+ * Actually now I think of it, it's possible that Ron *is* half the Plan 9
+ * userbase. Oh well. */
+static bool could_be_syscall(unsigned int num)
+{
+ /* Normal Linux SYSCALL_VECTOR or reserved vector? */
+ return num == SYSCALL_VECTOR || num == syscall_vector;
+}
+
+/* The syscall vector it wants must be unused by Host. */
+bool check_syscall_vector(struct lguest *lg)
+{
+ u32 vector;
+
+ if (get_user(vector, &lg->lguest_data->syscall_vec))
+ return false;
+
+ return could_be_syscall(vector);
+}
+
+int init_interrupts(void)
+{
+ /* If they want some strange system call vector, reserve it now */
+ if (syscall_vector != SYSCALL_VECTOR
+ && test_and_set_bit(syscall_vector, used_vectors)) {
+ printk("lg: couldn't reserve syscall %u\n", syscall_vector);
+ return -EBUSY;
+ }
+ return 0;
+}
+
+void free_interrupts(void)
+{
+ if (syscall_vector != SYSCALL_VECTOR)
+ clear_bit(syscall_vector, used_vectors);
}
/*H:220 Now we've got the routines to deliver interrupts, delivering traps
/* deliver_trap() returns true if it could deliver the trap. */
int deliver_trap(struct lguest *lg, unsigned int num)
{
- u32 lo = lg->idt[num].a, hi = lg->idt[num].b;
+ /* Trap numbers are always 8 bit, but we set an impossible trap number
+ * for traps inside the Switcher, so check that here. */
+ if (num >= ARRAY_SIZE(lg->arch.idt))
+ return 0;
/* Early on the Guest hasn't set the IDT entries (or maybe it put a
* bogus one in): if we fail here, the Guest will be killed. */
- if (!idt_present(lo, hi))
+ if (!idt_present(lg->arch.idt[num].a, lg->arch.idt[num].b))
return 0;
- set_guest_interrupt(lg, lo, hi, has_err(num));
+ set_guest_interrupt(lg, lg->arch.idt[num].a, lg->arch.idt[num].b,
+ has_err(num));
return 1;
}
/*H:250 Here's the hard part: returning to the Host every time a trap happens
* and then calling deliver_trap() and re-entering the Guest is slow.
- * Particularly because Guest userspace system calls are traps (trap 128).
+ * Particularly because Guest userspace system calls are traps (usually trap
+ * 128).
*
* So we'd like to set up the IDT to tell the CPU to deliver traps directly
* into the Guest. This is possible, but the complexities cause the size of
* this file to double! However, 150 lines of code is worth writing for taking
* system calls down from 1750ns to 270ns. Plus, if lguest didn't do it, all
- * the other hypervisors would tease it.
+ * the other hypervisors would beat it up at lunchtime.
*
- * This routine determines if a trap can be delivered directly. */
-static int direct_trap(const struct lguest *lg,
- const struct desc_struct *trap,
- unsigned int num)
+ * This routine indicates if a particular trap number could be delivered
+ * directly. */
+static int direct_trap(unsigned int num)
{
/* Hardware interrupts don't go to the Guest at all (except system
* call). */
- if (num >= FIRST_EXTERNAL_VECTOR && num != SYSCALL_VECTOR)
+ if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num))
return 0;
/* The Host needs to see page faults (for shadow paging and to save the
* fault address), general protection faults (in/out emulation) and
* device not available (TS handling), and of course, the hypercall
* trap. */
- if (num == 14 || num == 13 || num == 7 || num == LGUEST_TRAP_ENTRY)
- return 0;
-
- /* Only trap gates (type 15) can go direct to the Guest. Interrupt
- * gates (type 14) disable interrupts as they are entered, which we
- * never let the Guest do. Not present entries (type 0x0) also can't
- * go direct, of course 8) */
- return idt_type(trap->a, trap->b) == 0xF;
+ return num != 14 && num != 13 && num != 7 && num != LGUEST_TRAP_ENTRY;
}
/*:*/
/* Depending on the CONFIG_4KSTACKS option, the Guest can have one or
* two pages of stack space. */
for (i = 0; i < lg->stack_pages; i++)
- /* The stack grows *upwards*, hence the subtraction */
- pin_page(lg, lg->esp1 - i * PAGE_SIZE);
+ /* The stack grows *upwards*, so the address we're given is the
+ * start of the page after the kernel stack. Subtract one to
+ * get back onto the first stack page, and keep subtracting to
+ * get to the rest of the stack pages. */
+ pin_page(lg, lg->esp1 - 1 - i * PAGE_SIZE);
}
/* Direct traps also mean that we need to know whenever the Guest wants to use
* change stacks on each context switch. */
void guest_set_stack(struct lguest *lg, u32 seg, u32 esp, unsigned int pages)
{
- /* You are not allowd have a stack segment with privilege level 0: bad
+ /* You are not allowed have a stack segment with privilege level 0: bad
* Guest! */
if ((seg & 0x3) != GUEST_PL)
kill_guest(lg, "bad stack segment %i", seg);
* part of the Host: page table handling. */
/*H:235 This is the routine which actually checks the Guest's IDT entry and
- * transfers it into our entry in "struct lguest": */
+ * transfers it into the entry in "struct lguest": */
static void set_trap(struct lguest *lg, struct desc_struct *trap,
unsigned int num, u32 lo, u32 hi)
{
* to copy this again. */
lg->changed |= CHANGED_IDT;
- /* The IDT which we keep in "struct lguest" only contains 32 entries
- * for the traps and LGUEST_IRQS (32) entries for interrupts. We
- * ignore attempts to set handlers for higher interrupt numbers, except
- * for the system call "interrupt" at 128: we have a special IDT entry
- * for that. */
- if (num < ARRAY_SIZE(lg->idt))
- set_trap(lg, &lg->idt[num], num, lo, hi);
- else if (num == SYSCALL_VECTOR)
- set_trap(lg, &lg->syscall_idt, num, lo, hi);
+ /* Check that the Guest doesn't try to step outside the bounds. */
+ if (num >= ARRAY_SIZE(lg->arch.idt))
+ kill_guest(lg, "Setting idt entry %u", num);
+ else
+ set_trap(lg, &lg->arch.idt[num], num, lo, hi);
}
/* The default entry for each interrupt points into the Switcher routines which
/* We can simply copy the direct traps, otherwise we use the default
* ones in the Switcher: they will return to the Host. */
- for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++) {
- if (direct_trap(lg, &lg->idt[i], i))
- idt[i] = lg->idt[i];
+ for (i = 0; i < ARRAY_SIZE(lg->arch.idt); i++) {
+ /* If no Guest can ever override this trap, leave it alone. */
+ if (!direct_trap(i))
+ continue;
+
+ /* Only trap gates (type 15) can go direct to the Guest.
+ * Interrupt gates (type 14) disable interrupts as they are
+ * entered, which we never let the Guest do. Not present
+ * entries (type 0x0) also can't go direct, of course. */
+ if (idt_type(lg->arch.idt[i].a, lg->arch.idt[i].b) == 0xF)
+ idt[i] = lg->arch.idt[i];
else
+ /* Reset it to the default. */
default_idt_entry(&idt[i], i, def[i]);
}
-
- /* Don't forget the system call trap! The IDT entries for other
- * interupts never change, so no need to copy them. */
- i = SYSCALL_VECTOR;
- if (direct_trap(lg, &lg->syscall_idt, i))
- idt[i] = lg->syscall_idt;
- else
- default_idt_entry(&idt[i], i, def[i]);
}
+/*H:200
+ * The Guest Clock.
+ *
+ * There are two sources of virtual interrupts. We saw one in lguest_user.c:
+ * the Launcher sending interrupts for virtual devices. The other is the Guest
+ * timer interrupt.
+ *
+ * The Guest uses the LHCALL_SET_CLOCKEVENT hypercall to tell us how long to
+ * the next timer interrupt (in nanoseconds). We use the high-resolution timer
+ * infrastructure to set a callback at that time.
+ *
+ * 0 means "turn off the clock". */
void guest_set_clockevent(struct lguest *lg, unsigned long delta)
{
ktime_t expires;
return;
}
+ /* We use wallclock time here, so the Guest might not be running for
+ * all the time between now and the timer interrupt it asked for. This
+ * is almost always the right thing to do. */
expires = ktime_add_ns(ktime_get_real(), delta);
hrtimer_start(&lg->hrt, expires, HRTIMER_MODE_ABS);
}
+/* This is the function called when the Guest's timer expires. */
static enum hrtimer_restart clockdev_fn(struct hrtimer *timer)
{
struct lguest *lg = container_of(timer, struct lguest, hrt);
+ /* Remember the first interrupt is the timer interrupt. */
set_bit(0, lg->irqs_pending);
+ /* If the Guest is actually stopped, we need to wake it up. */
if (lg->halted)
wake_up_process(lg->tsk);
return HRTIMER_NORESTART;
}
+/* This sets up the timer for this Guest. */
void init_clockdev(struct lguest *lg)
{
hrtimer_init(&lg->hrt, CLOCK_REALTIME, HRTIMER_MODE_ABS);
projects / linux-2.6-omap-h63xx.git / blobdiff